Volcanic risk areas may be larger than previously thought, UB-led research suggests

A study led by UB geologist Greg A. Valentine on the potential reach of volcanic eruptions could have significant impact on how hazard assessments are conducted in areas prone to eruptions.

The research, “Lateral Extent of Pyroclastic Surge Deposits at Ubehebe Crater (Death Valley, California) and Implications for Hazards in Monogenetic Volcanic Fields,” was first published online in October in the American Geophysical Union’s Geophysical Research Letters.

Valentine, UB Distinguished Professor in the Department of Geology, College of Arts and Sciences, led a team of colleagues from the U.S. Geological Survey and University of Otago in New Zealand.

Many explosive eruptions are caused by interaction of hot molten rock and groundwater. These can produce ground-hugging currents of gas and particles known as pyroclastic surges. Historically, geologists have assessed the risk posed by potential pyroclastic surges as extending between .1 to 4 miles from the eruption site. In other words, people, vegetation and infrastructure located within the range — called a runout — are at significant risk.

These projections are based upon preserved geologic deposits from previous eruptions in the volcanic field.

However, Valentine’s research in the Ubehebe Crater in California’s Death Valley measured the surge deposits as extending nearly six miles.

Valentine notes that this was not an unusual eruption, but its deposits have been exceptionally preserved due to the dry and vegetation-poor environment. In addition, surges from magma-water explosions are likely to be cooler than other volcanic flows, which facilitates longer surge distances.

“Previous studies of surge runout distance had used the best data that were available at the time, which were based on deposits of volcanoes where similar eruptions occurred,” Valentine explains. “Most of these used a few kilometers, but here just because of the good preservation in Death Valley, we see evidence for a wider area of impact.”

He suggests that future hazard assessments in volcanic fields allow for runout up to about 9 miles, and that civic leaders should consider that number when planning evacuations when a volcano is expected to erupt.

Even at low flow speeds and relatively low temperatures, volcanic surges pose a risk of asphyxiation and burns for humans and animals, and can damage infrastructure such as air intakes and internal combustion engines. Therefore, using more realistic estimates of the potential reach of a surge is crucial to hazard assessments and emergency planning in areas that might be subjected to such volcanic activity.

“If you live in a large city, having a hazard that extends 10 kilometers from a crater is very different from one that extends only 2 kilometers from the crater,” Valentine says. “The volcano could affect a much larger populated area and much more infrastructure.”

For the study, Valentine conducted numerical simulations at UB’s Center for Computational Research.

The work was funded by U.S. National Science Foundation Grant EAR-2035260 to Valentine, the U.S. Geological Survey, and by support from DEVORA (Determining Volcanic Risk for Auckland). Field research was conducted with permission of Death Valley National Park.